Chain saw



FIG. 1 is a perspective view of our chain saw design;

FIG. 2 is a left view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a bottom side view thereof;

FIG. 5 is a front view thereof;

FIG. 6 is a back view thereof; and,

FIG. 7 is a top view thereof.

The broken lines shown in the drawings form no part of the claimed design. 

The ornamental design for a chain saw, as shown and described. 